A variety of heart valve prostheses have been developed for use in hearts, such as human or animal hearts. The typical heart value prosthesis generally includes a main body portion having an annular shape and a central passage for blood flow. One or more leaflet occluders are mounted to the annular body for pivotable movement within the central passage. Such heart valve assemblies operate hemodynamically in conjunction with the pumping action of the heart for effective replacement of a defective natural heart valve.
A common heart valve construction is the bi-leaflet design in which two leaflet occluders are pivotably mounted in the annular body in an opposed relationship. The leaflet occluders are mounted such that when the heart valve is closed, each leaflet occluder covers approximately half of the valve opening or passage. Typically, each leaflet occluder is generally semi-circular in shape and includes a rounded exterior which engages an inner surface of the main body that defines the central passage. Each leaflet occluder also includes a generally linear edge portion designed to move proximate the linear edge portion of the opposing leaflet occluder when the valve is closed. Each leaflet occluder is mounted for pivotable movement about an axis disposed generally parallel with the linear edge.
In operation, as blood pressure rises in response to heart contraction, the leaflet occluders are pivoted from a closed position to an open position. In the open position, blood flows past the leaflet occluders through the heart valve passage. When the heart contraction is complete, however, the blood tends to flow in the opposite direction in response to pressure in the aorta. This causes the leaflet occluders to close and thereby maintain a pressure in the arterial system. Effectively, this type of heart valve prosthesis operates in substantially the same manner as a natural human heart valve.
Conventional leaflet occluders include opposing tabs or ears that are received in corresponding recesses formed in the interior surface defining the flow passage. Each pair of opposed recesses constrain the leaflet occluder mounted therein, and the walls of the recesses serve as stops to limit the pivoting motion of the leaflet occluders at closed and open positions. Exemplary prior art designs are illustrated and described in such patents as Hanson et al., U.S. Pat. No. 4,276,658, Bokros, U.S. Pat. No. 4,689,046, and Campbell, U.S. Pat. No. 5,147,390. Such prior art valves have generally proved to be very reliable, and have a projected life expectancy exceeding that of the patient. However, it is desirable to continually increase or enhance the performance characteristics of heart valve prostheses.
For example, problems can develop because of the design of the recesses for receiving the leaflet occluder ears. In many applications, it is desirable to design recesses with a contour providing at least two stops that act against the leaflet ear to limit the pivotable motion of a given leaflet occluder. By separating the stops that act against the ear, the angle at which the leaflet occluders close and/or open can be better controlled. The Hanson et al. reference and the Bokros reference cited above utilize recesses having narrowed throat regions and expanded outlying regions to provide at least two stops separated by a given distance that act against the leaflet occluder ear to limit a given pivoting motion.
Though such designs provide two stopping surfaces, they are typically limited by wall surfaces that are generally perpendicular to the interior surface that defines the blood flow passage of the heart valve. Such perpendicular surfaces often exist throughout the throat region of the recess and limit the ability of the blood to freely flow through the recessed area. As a result, blood clotting can occur in the vicinity of the pivot recesses.
It would be advantageous to provide a heart valve prosthesis with uniquely designed leaflet occluder pivot recesses able to facilitate better blood flow characteristics while providing stable control of the opening and closing of the leaflet occluders.